Modular small arms, especially rifles, such as the M16 and its civilian variant the AR-15, have been incredibly popular with militaries, law enforcement organizations and civilians alike. Their popularity is due, in large part, to their ability to be seemingly endlessly customized, allowing them to serve in a wide variety of roles. This versatility allows cost savings, through reductions in the purchase of specialized firearms, and inspires operator confidence through familiarity with the platform.
One of the common customizations to such firearms is the replacement of the factory stock. In cases where such a rifle is sold with a fixed stock, it may be replaced with an adjustable one, allowing the user, during use, to adjust the overall length of the rifle to suit different situations that may be encountered. For example, in military use a room clearing situation may be encountered during the same mission as a medium-range (˜200-400 yards) target engagement. The room clearing situation may dictate as short of an overall length as possible to maximize the maneuverability of the rifle in what is likely to be tight quarters while a longer overall length may provide better handling characteristics in the medium-range engagement situation.
Even in cases where the rifle is provided with a factory adjustable stock, another might be added that provides a larger range of adjustment. Those that allow for the shortest possible overall length when fully collapsed while maintaining similar or greater overall length to factory-provided solutions when fully extended are especially useful in increasing the versatility of the rifle.
While modular small arms are designed to accommodate a wide range of components, it is sometimes necessary to alter the factory design of various elements in addition to the component being replaced to provide the best performance possible. One instance where this is the case is when attempting to provide the most compact adjustable stock possible, where the factory design of the receiver extension of most popular modular small arms prevents collapsing of the stock beyond a certain point, at least practically, since the receiver extension would protrude from the stock if allowed to collapse beyond a certain point. Unfortunately, current state of the art solutions that provide such benefits also interfere with field-stripping of the firearm and require replacement of the bolt carrier group, receiver extension and/or buffer with one of a proprietary design.
Such compromises require additional operator training in the new field-stripping techniques and reduce the availability of replacement parts in the field. They may also reduce operator confidence in the firearm itself. Additionally, such compromises can reduce the operator's ability to customize further aspects of the firearm, such as the buffer weight used, since current state of the art designs often utilize a one-piece bolt carrier group and buffer assembly.
Another problem with such compact designs is that they tend to be less resistant to collapse, when at full extension, than standard designs. This is because standard stock designs utilize the receiver extension for positioning, which is drastically shortened in ultra-compact stock designs, while current state of the art ultra-compact stock designs use guide rods, which are mounted on either side of the modified receiver extension to support the stock and enable length-adjustments. These guide rods typically have straight cuts in a top portion at substantially equal distances along their length. These cuts engage a retractable protrusion in the stock assembly to lock the stock to a given position on the guide rods. Such a system can allow the stock to collapse under hard use, such as during fully-automatic fire, since the contact area between the protrusion and guide rod cuts is limited by the depth of cut that may be made without unduly weakening the guide rods.
What is needed, therefore, is a compact and robust stock for modular small arms that allows for routine maintenance procedures to be carried out without substantial additional training.